Process for stopping peptisation of polychloroprene latex



United States Patent 3 488,313 PROCESS FOR STO PPING PEPTISATION OF POLYCHLOROPRENE LATEX Anthony Archibald Sparks, Epsom Downs, Surrey, and

range 3 to 5 hours. The preferred temperature is in the range 40 to 50 C.

It is essential to adjust the temperature of the latex to less than 20 C. to stop the peptisation. It is preferred to carry out the process by adjusting the temperature of the Robert Charles Moore, Sutton, Surrey, England, as- 5 signors to The Distillers Company Limited, Edinburgh, latex to between to 12 C.

Scotland, at British company It is surprising that adjusting the temperature of the N0 Dlawing- Continuation-impart of application latex to less than 20 C. immediately stops the peptisation 313 32 83, 1964- This application 1966, reaction. It would have been natural to assume that lowerer. 0. Claims priority, application Gregt Britain July 3 1963, 10 Itlhe temperature would merely slowed the reaction /6 The present invention provides a process for stopping us. C]. Cosd 5/02 7/00 4 Claims the stated peptisation process for sulphur modified polychloroprene at any desired stage, thus enabling the use of relatively high concentration of sulphur in the original polymerisation process. Furthermore rubbers having par- ABSTRACT OF THE DISCLOSURE ticularly desirable properties can be obtained from the Peptization of sulphur modified polychloroprene latex i ll ti d 1 may be stopped according to a two step process which com- Exam 1e 1 prises peptizing an aqueous latex of sulphur modified poly- P chloroprene at a temperature in the range of 35 C. to 60 An aqueous 11teX of a curable Sulphur modified P C. with a tetra alkyl thiuram disulphide and a dialkyl chloroprene i g 3 P o 1 1.0 was prepared uslng well dithiocarbamate and thereafter adjusting the temperature knpwn emulslfm polymensatlon procedulcs Whldi a of the peptized latex before peptization is complete to a mmor proPomon of Sulphur was present temperature less than 20 C., such temperature being greati i gsgi g ogsggggf jfi3 g: gg glz g si g er than that required to cause the latex t0 coa ulate. proximately 85 conversion y the addition of 0.1%

(weight/weight on monomer) dimethyl ammonium dimethyl dithiocarbamate.

The present invention relates to a process r S PP The temperature of samples of the latex were adjusted certain Processes for the peptisation of ip f' 9 to approximately 40 C. which is that preferred for peptisapo ychlo op e- The application is a contlnuatlon-m'part tion and then a tetraethyl thiuram disulphide emulsion appli at of application 5611 374,287 filed on was added to each latex sample to give a concentration of June 11, 1964, now abandoned. thiuram of 2.0% (weight/ weight on monomer).

Y the term Sulphur modified Polychlomprene 1S meant A sample of the latex was allowed to peptise for 6 hours throughout this specification any synthetic rubber formed at a temperature f C d h h temperature was y Polymerising 2-Ch1f0-1,3-buiadi$ne 0T -L adjusted to 10 to 12 C. By way of comparison a second ut n and a copoiymefisabie monomer in aqueous sample of the latex was allowed to peptise for 24 hours at emulsion in the presence of sulphur. By the term petisaa temperature of 40 C. At frequent intervals the pH value tion is meant throughout this specification the breakdown 40 of a portion of each latex sample was adjusted to 7.0 by or partial breakdown of the sulphur modified polychloroaddition of 10% acetic acid, the rubber isolated by freeze prene to give a product having the desired degree of plascoagulation and dried in an air oven. The change in ticity for processing by the methods used commercially. Mooney viscosity of the rubber isolated in relation to the The process for the peptisation of sulphur modified polypeptisation time of the latex is shown in Table 1 which chloroprene according to the present invention comprises illustrates that the peptisation reaction is stopped by adpeptising at a temperature in the range 35 to 60 C. an justing the temperature to 10 to 12 C.

TABLE 1 Temper- Mooney viscosity, (ML!) after ature of peptisation 1. 5 3. 5 6 8 12 18 24 Sample 111 0. hours hours hours hours hours hours hours Control 40 113 71 54 47 44 42 41 Example 40 113 71 54 54.5 54 54.5 54

1 For 6 hours then 1012 C. aqueous latex of a sulphur modified polychloroprene with 55 E l 2 a tetra alkyl thiuram disulphide and a dialkyl dithiocarbamate and adjusting the temperature of the peptised latex before peptisation is complete to a temperature less than 20 C. and greater than the temperature which is sufficient to cause the latex to coagulate.

Most suitably the alkyl groups in the tetra alkyl thiuram disulphide and the dialkyl dithiocarbamate have 1 to 6 carbon atoms. Most suitably the dialkyl dithiocarbarnates are the dialkyl ammonium dialkyl dithiocarbamates.

The preferred peptising systems are those containing tetra ethyl thiuram disulphide and dimethyl ammonium dimethyl dithiocarbamate. Most suitably the temperature at which peptisation is carried out should be such as to give a rate of peptising reaction which gives rise to the desired product in a commercially acceptable time, for example a minimum of about 1 hour and preferably a time in the An aqueous latex of a curable sulphur modified polychloroprene having a pH of 11 was prepared and peptised in accordance with the procedure described in Example 1.

A control sample of the latex was peptised for 12 hours at a temperature of 40 C. Another sample (a) of this latex was peptised for 4 hours at 40 C. and then the temperature adjusted to 12 to 20 C. A further sample (b) of the sample of the latex was peptised for 4 hours at 60 C. and then the temperature adjusted to 10 to 12 C. The samples were then treated in a similar manner to that described in Example 1 and the changes in Mooney viscosity of the rubber isolated in relation to peptisation time for each sample is shown in Table 2. The results illustrate that the peptising reaction is stopped by adjusting the temperature to 10 to 12 C.

TABLE 2 Mooney viscosity, (ML4') after- Temperature of peptisation 1 4 6 8 12 Sample in 0, hour hours hours hours hours Control 40 48 41 36 31 Sample (a) 40 for 4 hours then 12-20 C 46 43 43 43 60 for 4 hours then l-l2 0--.- 45 45 34 33 34 Example 3 An aqueous latex of a curable sulphur modified poly- 10 chloroprene having a pH of 11 was prepared and peptised in accordance with the procedure described in Example 1.

A control sample 1 of latex was peptised for 12 hours at 40 C., a second control sample 2 was peptised for 12 hours at a temperature of 20 C. and a third sample (a) peptised for 3 hours at 40 C. and then the temperature A control sample of the latex was peptised for 8 /2 hours at a temperature of 50 C. A second sample of the latex was peptised at 50 C. for 5 hours and then the temperature adjusted to 10 to 12 C. The samples were treated in a similar manner to that described in Example 1 and the changes in Mooney viscosity of the rubber isolated in relation to peptisation time for each sample is shown in Table 5.

was adjusted to 10 to 12 C. The samples were then treated in a similar manner to that described in Example 1 and the changes in Mooney viscosity of the rubber isolated in relation to peptisation time for each sample is shown in Table 3.

This data given illustrates that where the latex is first peptised at 40 C. peptisation is stopped by adjusting the temperature to 10 to 12 C. and that by way of comparison peptisation will take place at a temperature of C. when the latex has not been initially peptised at higher temperatures.

An aqueous latex of a curable sulphur modified polychloroprene having a pH of 11 was prepared and peptised in accordance with the procedure described in Example 1.

A control sample of latex was peptised for 8% hours at 35 C., a second sample of the latex was peptised at 35 C. for 5 hours and then the temperature adjusted to 10 to 12 C. The samples were then treated in a similar manner to that described in Example 1 and the changes in Mooney viscosity of the rubber isolated in relation to peptisation time for each sample is shown in Table 4.

2. A process as claimed in claim 1 wherein the temperature is adjusted to between 10 C. to 12 C.

3. A process as claimed in claim 1 wherein the latex is peptised with tetra ethyl thiuram disulphide and dimethyl ammonium dimethyl dithiocarbamate.

4. A process for the production of a peptized sulphur modified polychloroprene latex which comprises (a) peptizing at a temperature in the range of 3560 C. an aqueous latex of sulphur modified polychloroprene with a tetra alkyl thiuram disulphide and a dialkyl dithiocarbamate, (b) stopping the peptization by lowering the TABLE 4 Mooney viscosity, (ML4) aiter- Temperature of 4 5 5. 5 8. 25 Sample peptisation in 0. hours hours hours hours Control 35 79 58 Example 35 for 5 hours then 1012 C. 82 70 68 70 Example 5 An aqueous latex of a curable sulphur modified polychloroprene having a pH of 11 was prepared and peptised in accordance with the procedure described in Example 1.

temperature of the peptized latex before peptization is completed to a temperature of less than 20 C. and greater than the temperature which is sufficient to cause the latex 5 6 to coagulate and, (c) maintaining the latex below 20 C. 3,318,832 5/1967 Sparks et a1. 26079.5 while the sulphur modified polychloroprene is isolated 3,320,201 5/1967 Sparks et a1. 26079.5 therefrom.

References Cited JAMES A. SEIDLECK, Primary Examiner UNITED STATES PATENTS 5 US Cl X'R 3,105,055 9/1963 AhO 2 79- 26030.8, 79.5 

